Typically, liver tissue receives oxygen and nourishment through two types of blood vessels: one is the portal vein that comes via the small and large intestines, and the other is the hepatic artery that directly arises from the aorta. Normal liver tissue is supplied with blood from both hepatic artery and portal vein, and tumor tissue is supplied with blood from the hepatic artery.
Transcatheter arterial chemoembolization (TACE), which is one of non-invasive techniques that are most frequently carried out for hepatocellular carcinoma (HCC) treatment, is a technique for cutting off arterial blood flow by inserting a catheter into the hepatic artery, injecting Lipiodol, which is an oily contrast medium mixed with an anti-cancer agent, through the catheter, and then inducing embolism. Alternatively, in some cases, an anti-cancer agent may be directly injected into the hepatic artery without the induction of embolism. With the TACE procedure, it is possible to accomplish selective tumor necrosis without great damage to normal liver tissue of a patient. The TACE procedure has a wide application range because it can be applied as long as serious jaundice or ascites does not appear, regardless of the stage of HCC. Up to now, the TACE procedure has been known as a method that contributes to an increase in the survival rate of HCC patients, because it has less limitations in the treatment indications for HCC and is allowed to perform for inoperable HCC patients. However, the procedure has a problem in that the treatment should be carried out several times because a tumor recurs frequently.
Comparison between different phase images of multi-phase (e.g., the pre-contrast images and post-contrast images acquired in the arterial phase, portal phase and equilibrium phase) helical or multi-detector computed tomography (CT) of the liver has been used to detect a residual/recurrent tumor in HCC patients who underwent the TACE procedure as a conventional detection method. For example, by comparing the pre-contrast images with the multi-phase post-contrast images, it is possible to detect a portion, which shows arterial enhancement and delayed wash-out, from a region of interest (ROI) within a Lipiodol-retained HCC as a residual/recurrent tumor portion.
Such a conventional detection method has problems in that it is difficult to perform accurate matching and comparison of a suspicious region between different phases because of a patient's respiration and also it is difficult to diagnose a residual/recurrent tumor in a portion other than the ROI within a Lipiodol-retained HCC.